Now, finally, the election is upon us. And now there is a chance for a once-in-a-half-century, perhaps even once-in-a-century political realignment. There is a chance to say goodbye to a politics built around tribalism and to move into a new chapter in American history.

I'll keep this short. From the civil war onwards, Democrats controlled America's southern states and used their power to enforce a rigid apartheid system. Southern Democrats remained a vital part of any national Democratic coalition, and hence, even under otherwise radical administrations such as those of Franklin Delano Roosevelt, segregation was never seriously challenged. The "peculiar institution" of slavery was ended by the Yankee victory in the civil war, but the almost equally peculiar institution of race politics and the division of society into racial castes persisted.

For reasons too convoluted to go into here, in the 1960s the national Democratic party embraced civil rights. And as the legal architecture of Jim Crow was dismantled and more African-Americans were registered to vote, reluctantly, at least at first, white southern Democrats began to reach out to these empowered constituents. Eventually African-Americans became a core part of the party's identity.

The Republicans sensed an opportunity and began aggressively courting conservative southern whites aggrieved by these changes. And in one of the country's more remarkable transferrals of political allegiance, in the space of a couple electoral cycles Dixie went from being Democrat to being Republican. And it has remained so ever since.

A core part of the Republican party's national coalition, in many ways the south has altered the GOP at least as much as the GOP has altered it. Lincoln's party went from being a party of moderate social reform to being almost revolutionary in its right-wing, conservative fervour; from being a party led by east coast Brahmins to being a party of born-again populists. It's the southern Republican party that so stridently pushed economic deregulation; that broke organised labour – in addition to opposing racial equality, historically southern political elites were notoriously anti-union; that eviscerated the minimum wage; that attempted to shatter church-state boundaries in a myriad of ways. It's the southern-dominated party that made opposition to abortion access a lynchpin wedge issue, and that has tried to do the same in recent years by touting a constitutional amendment to ban gay marriage.

But, always, the centrality of race has remained, sometimes bubbling up to the surface, sometimes partially camouflaged. For decades, the Republican party has played an array of race cards to win and maintain power. In 1968, Nixon won the keys to the White House at least in part because of his appeal to what he later labelled a "silent majority", a conservative bloc of voters hostile to civil rights and eager to conflate black citizens with crime. In 1980, Reagan used images of African-American "welfare queens" to go after liberal defenders of government social programmes. Eight years later, Bush Sr used the notorious Willie Horton ads - photos of an African-American prisoner who had been furloughed from a Massachusetts prison while Mike Dukakis was governor, and who had then gone on to rape a white woman - to destroy his Democratic opponent. In 2000, Bush defeated McCain in the GOP primaries largely on the back of racially inflammatory robocalls in South Carolina insinuating that McCain had illegitimately fathered a black daughter.

Eight years on, McCain, now the nominee, has done everything possible to cast aspersions on Obama's Americanness. While colour is never explicitly mentioned, it's the subtext in many of his and Sarah Palin's speeches, as well as in the numerous robocalls that have blitzed residents in southern states over the past two months.

In the last few days, Pennsylvania - one of only two Democratic states from the 2004 election thought to be within McCain's reach - has been flooded by television ads once again seeking to correlate Obama to the inflammatory preacher Jeremiah Wright. Palin supporters have been filmed holding toy monkeys with Obama signs on them at her rallies. And a miasma of racist rhetoric hangs over much of the campaigning by local Republican party operatives in many southern states. One Georgia representative even used the word "uppity" in early September to describe the Ivy League-educated Barack and Michelle Obama – a term almost exclusively used by southern whites to refer to blacks who aren't content with accepting a lowly lot in life.

We'll shortly know whether these tactics worked. If they did, it will be a cultural catastrophe. In poll after poll, Obama outperforms McCain on all the key issues: the economy, foreign policy, environmental issues, healthcare plans and so on. Polls show he beat McCain in all three of their face-to-face debates. And, as significantly, several polls that attempted to measure the "likeability" factor also gave Obama an edge. He's seen as someone more voters would prefer to have beers with, watch football with, be a teacher to their children. In other words, when it comes to both ideas and personality, Obama wins.

If democracy is simply a competition of ideas varnished by a sense of personal charm evinced by its lead figures, Obama's the next president. But democracy is more than that. Unfortunately, tribalism has a powerful hold on the process. A significant number of people - despite an unprecedented year-long national conversation about race and culture and American identity - still have a gut-check problem with voting for a black man.

If McCain wins, tribalism wins. The southern gamble, that race will always remain central to the nation's political decision-making process, that race will always trump economic common sense, pays off. And the American dream takes a rabbit punch to the kidneys that will take decades to recover from.

If Obama wins, however, taking some southern states and bringing enough new voters to the polls that several Senate seats in the region also go blue, then at long last the possibility of a truly post-racial political system comes one enormous step closer to fruition.